In recent years, a spectral imaging camera acquiring a spectroscopic spectrum of a subject and image data of the subject has been developed and widely applied to various fields.
For example, in JP-A-2009-39280 (Patent Document 1), there is disclosed a technique in which a spectrum of emitted light or reflected light from a lesion such as a cancer is measured the thereby identify the lesion of a subject in an endoscope for examining the inside of an organ.
In the endoscope, light from the subject collected by a lens is incident on a diffraction grating through a slit. Then, the light separated by the diffraction grating forms an image on an imaging unit by a lens arranged in the subsequent stage to thereby acquire a spectroscopic spectrum of the light from the subject.
In JP-A-2005-337793 (Patent Document 2), there is disclosed a technique in which different light receiving areas are provided for acquiring the image as well as for acquiring the spectroscopic spectrum respectively. That is, light from the subject is incident on the diffraction grating and zero-order light forms an image on the light receiving area dedicated for the zero-order light, thereby acquiring the image of the subject. Additionally, first-order light of the diffraction grating is received by the light receiving area dedicated for the first-order light, thereby detecting the spectroscopic spectrum.